This invention relates to a magnetic device which makes possible the alignment of magnetic poles having a high precision as is required for a magnet roller for a plain paper copier.
Heretofore, there has been used a magnet roller for a plain paper copier wherein cylindrical or bar shape sintered ferrite magnets are aligned around a shaft. However, there has been a recent trend towards adopting a so-called bonded magnet which comprises mixing and dispersing ferro-magnetic fine powders in rubbers or resin matrices of plastic or the like because of difficulties in treating sintered magnets in an assembling step caused by the fragility of the sintered magnet, usually the result of crack or breakage, etc. caused by an impact or a vibration after assembling combined with the high cost of sintered magnets. Although the bonded magnet has several characteristics not present in the sintered ferrite magnet, said bonded magnet has a defect which decreases the magnetic characteristics due to its fundamental nature wherein the magnetic substance is diluted by the resin matrices. For avoiding this defect, an "orientation" is adopted which arranges the C-axis direction in the ferrite crystal, as a method of increasing the characteristic of the magnet. In addition, there exists a method of providing a high magnetic flux density by improving the permeance of the magnet, the bonded magnet having a resinous nature, thereby being able to easily form an intended profile cross section.